A unique feature of the so-called free electron laser (FEL) is its precise, tunable beam which can be used for surgical lesioning/cutting. Specifically, the power deposition and wave length of FEL-energy can be controlled so that there is very little bleeding associated with the cut. Preliminary histological studies demonstrate minimal bleeding and tissue damage in the brain after FEL-induced cuts. It is currently unknown how the power deposition from the FEL affects the surrounding brain tissue. For example, although very little bleeding/tissue trauma is associated with the cut itself, edema may be widespread. Edema formation is not easily quantitated by conventional histology. We will use magnetic resonance microscopy to evaluate the amount of edema which forms around a FEL-induced cortical cut. We will compare these lesion with that induced by a biopsy-puncture. The studies will be performed on normotensive and spontaneously hypertensive rats.